Refrigerant handling system with inlet refrigerant liquid/vapor flow control

ABSTRACT

A refrigerant recovery system includes a compressor and an evaporator connected to the compressor inlet for evaporating refrigerant passing therethrough to the compressor inlet from refrigerant equipment under service. A sensor is coupled to the system input for detecting presence of liquid phase refrigerant. A valve is connected to the compressor inlet in parallel with the evaporator for bypassing refrigerant from the evaporator to the compressor inlet when the sensor indicates that liquid refrigerant is absent at the system input. The liquid refrigerant sensor takes the form of an open canister between the system input and the evaporator, and a liquid level sensor coupled to the canister for sensing level of liquid refrigerant collected within the canister. A solenoid valve is connected in parallel with the evaporator, and is responsive to the liquid level sensor for opening the valve and bypassing the evaporator in the absence of liquid refrigerant within the canister. In this way, when input refrigerant is already in vapor phase, such refrigerant is bypassed to the compressor inlet, eliminating undesirable superheating of the refrigerant within the evaporator.

The present invention is directed to systems for handling refrigerant ineither liquid, vapor or mixed liquid/vapor phase, and more particularlyto systems for recovering refrigerant in liquid and/or vapor phase fromrefrigeration equipment such as air conditioning and heat pumpequipment.

BACKGROUND AND OBJECTS OF THE INVENTION

Many scientists contend that release of halogen refrigerants into theatmosphere deleteriously affects the ozone layer that surrounds andprotects the earth from ultraviolet solar radiation. Recentinternational discussions and treaties, coupled with related regulationsand legislation , have renewed interest in devices for recovery andstorage of used refrigerants from refrigeration equipment for laterpurification and reuse or for proper disposal. U.S. Pat. No. 4,261,178,assigned to the assignee hereof, discloses a refrigerant recovery systemin which the inlet of a compressor is coupled through an evaporator andthrough a manual valve to the refrigeration equipment from whichrefrigerant is to be recovered. The compressor outlet is connectedthrough a condenser to a refrigerant storage container. The condenserand evaporator are combined in a single assembly through which coolingair is circulated by a fan. Content of the storage container ismonitored by a scale on which the container is mounted for sensingweight of liquid refrigerant in the container, and by a pressure switchcoupled to the fluid conduit between the condenser and the container forsensing vapor pressure within the storage container. A full-containercondition sensed at the scale or a high-pressure condition sensed at thepressure switch terminates operation of the compressor motor. A vacuumswitch is positioned between the inlet valve and the evaporator forsensing evacuation of refrigerant from the refrigeration system andautomatically terminating operation of the compressor motor.

U.S. Pat. Nos. 4,768,347 and 4,809,520, also signed to the assigneehereof, discloses a refrigerant recovery system that includes acompressor having an inlet coupled through an evaporator and through asolenoid valve to the refrigeration equipment from which refrigerant isto be withdrawn, and an outlet coupled through a condenser to arefrigerant storage container or tank. The refrigerant storage containeris carried by a scale having a limit switch coupled to controlelectronics to prevent or terminate further refrigerant recovery whenthe container is full. The scale comprises a platform pivotally mountedby a hinge pin to a wheeled cart, which also carries theevaporator/condenser unit, compressor, control electronics, andassociated valves and hoses.

Although the systems disclosed in the noted patents address and overcomeproblems theretofore extant in the art, further improvements remaindesirable. For example, a problem remains relative to controlling inletflow to the evaporator and compressor so as to maximize overall recoveryspeed and efficiency for either liquid, vapor or mixed liquid/vaporphase inlet refrigerant, while ensuring that refrigerant at thecompressor is in vapor phase so as to prevent slugging at thecompressor. It is also desirable to control the inlet refrigerant flowin such a manner as to minimize superheating of the refrigerant in theevaporator, which reduces efficiency of the handling system and theamount of refrigerant that can be pumped therethrough.

It is therefore a general object of the present invention to provide arefrigerant handling system, such as a refrigerant recovery system, thatincludes the capability of handling inlet refrigerant in either vaporphase, liquid phase or mixed liquid/vapor phase, that is adapted tooptimize flow of refrigerant therethrough a function of inletrefrigerant phase, and that ensures that refrigerant at the compressorinlet is in vapor phase so as to prevent slugging and possible damage tothe compressor. Another and related object of the present invention isto provide a refrigerant handling system of the described character thatoperates automatically without operator invention. A further object ofthe present invention is to provide a refrigerant handling system of thedescribed character in which flow of refrigerant to the evaporator isoptimized for enhanced heat exchange with the refrigerant condenserwhile substantially reducing or preventing superheating of therefrigerant.

SUMMARY OF THE INVENTION

A refrigerant handling system in accordance with the present inventionincludes a compressor and an evaporator connected to the compressorinlet for evaporating refrigerant from a refrigerant source passingtherethrough to the compressor inlet. In accordance with a first aspectof the invention, a sensor is coupled to the system input for detectingpresence of liquid phase refrigerant. A valve is connected to thecompressor inlet in parallel with the evaporator for bypassingrefrigerant from the evaporator to the compressor inlet when the sensorindicates that liquid refrigerant is absent at the system input. In oneembodiment of the invention, the liquid refrigerant sensor takes theform of an open canister between the system input and the evaporator,and a liquid level sensor coupled to the canister for sensing level ofliquid refrigerant collected within the canister. A solenoid valve isconnected in parallel with the evaporator, and is responsive to theliquid level sensor for opening the valve and bypassing the evaporatorin the absence of liquid refrigerant within the canister. In anotherembodiment of the invention, the sensor comprises a sight glass foroperator observation of refrigerant phase passing to the evaporator, anda solenoid valve coupled to a manual switch for selectively bypassingthe evaporator when only vapor phase refrigerant is observed at thesight glass. In this way, when input refrigerant is already in vaporphase, such refrigerant is bypassed to the compressor inlet, eliminatingundesirable superheating of the refrigerant within the evaporator.

In accordance with a second aspect of the present invention, which maybe used separately from or in combination with the first aspect of theinvention discussed hereinabove, a condenser is connected to thecompressor outlet in heat exchange relationship with the evaporator. Theevaporator/condenser unit comprises a closed canister in which thecondenser takes the form of a coil disposed within the canister at alower portion of the canister volume. A liquid refrigerant level sensoris operatively coupled to the evaporator/condenser canister fordetecting a level of liquid phase refrigerant in the evaporator sectionand covering or encompassing the condenser coils. The level sensor isconnected to a solenoid valve at the evaporator inlet of theevaporator/condenser for admitting refrigerant to the internal canistervolume so as to maintain level of refrigerant just covering thecondenser coil. In this way, liquid refrigerant is maintained within thecanister at a level for optimum heat exchange with the condenser coil.Most preferably, a second liquid refrigerant level sensor is positionedbelow the first sensor for detecting decrease of liquid refrigerant to asecond lower level, and for automatically opening a second solenoidvalve parallel of the first valve for increasing flow of refrigerant tothe canister. In this way, if the input refrigerant is substantially invapor phase, the flow of refrigerant vapor to the compressor inlet willbe greatly increased. In a presently preferred implementation of theinvention in a refrigerant recovery system, the compressor outlet isconnected through the condenser to a refrigerant storage container, withthe condenser functioning for at least partially condensing orliquefying refrigerant fed therethrough to the storage container.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objects, features and advantagesthereof, will be best understood from the following description, theappended claims and the accompanying drawings in which:

FIG. 1 is a schematic diagram of a refrigerant recovery system inaccordance with one presently preferred embodiment of the invention;

FIG. 2 is a fragmentary schematic diagram of a portion of the systemillustrated in FIG. 1 showing a modified embodiment of the invention;and

FIG. 3 is a fragmentary schematic diagram of a portion of the systemillustrated in FIG. 1 showing a second modified embodiment of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a refrigerant recovery system 10 in accordance with apresently preferred embodiment of the invention as comprising an inputsolenoid valve 12 coupled to a connector 14 for connection to equipmentunder service from which refrigerant is to be withdrawn. Refrigerantfrom valve 12 is fed through a filter 16 and a check valve 18 to anaccumulator 20 for separating liquid phase refrigerant from vapor phaserefrigerant. A pressure sensor 17 is connected between filter 16 andcheck valve 18. Accumulator 20 comprises a canister 22 having an openinternal volume. Refrigerant from check valve 18 is fed into the upperportion of the canister volume, and an outlet port from the upperportion of the canister volume is connected through a solenoid valve 24to an oil separator 26. A refrigerant liquid level sensor 28 of anysuitable type is positioned within the lower portion of canister 22, andis operatively connected to solenoid valve 24. When liquid refrigerantis present at sensor 28, valve 24 is closed. On the other hand, whensensor 28 detects absence of liquid refrigerant within canister 22,valve 24 is opened.

A liquid refrigerant port at the lower portion of canister 22 isconnected through a flow control valve 30 to the inlet of the evaporatorsection 32 of a combined evaporator/condenser unit 34. Control inputs tovalve 30 are connected to refrigerant bulbs 36, 38 positioned at theinlet and outlet sides of evaporator 32 respectively. Structure andfunction of control valve 30 and bulbs 36, 38 are disclosed in detail inco-pending application Ser. No. 07/641,433 assigned to the assigneehereof, to which reference may be made for more detailed discussion. Theoutlet of evaporator section 32 is connected to the inlet of oilseparator 26. Thus, when liquid phase input refrigerant is detected bysensor 28, valve 24 is closed, and the liquid refrigerant ispreferentially fed through evaporator section 32 to oil separator 26.However, when liquid phase refrigerant is absent at the system input,sensor 28 opens valve 24, which thus bypasses evaporator 32 and feedsvapor phase refrigerant directly to oil separator 26.

Refrigerant is fed from oil separator 26 through a filter/dryer unit 40for removing water vapor, acid and other contaminants from refrigerantpassing therethrough, to the inlet of a compressor 42 driven by a motor44. Oil collected in separator 26 is selectively drained by a valve 46to a catch bottle 48. The outlet of compressor 42 is connected to acompressor oil separator 50, from which return oil is fed through afilter 52 and a solenoid valve 54 to the compressor inlet. Therefrigerant outlet of separator 50 is connected through a check valve 56to a manual valve 58, which may be placed in the configuration as shownfor normal recovery operation, or in an opposing configuration forclearing refrigerant from the system components. Valve 58 is connectedthrough a coil 60 that surrounds oil separator 50 in heat exchangerelation with the separator wall and refrigerant within the separator.The general structure and function of separator 50 with coil 60 aredisclosed in U.S. Pat. No. 5,042,271, to which reference may be made forfurther details. The general structure and function of valve 58 isdisclosed in co-pending application Ser. No. 07/681,365 assigned to theassignee hereof, to which reference may be made for further details.

The outlet end of coil 60 is connected through the condenser section 62of evaporator/condenser unit 34, and thence through a coil 64 thatsurrounds oil separator 26. The outlet end of coil 64 is connectedthrough a chamber 66 in heat exchange relationship with refrigerantcaptured within a bulb 68. The outlet side of chamber 66 is connectedthrough an air purge tank 70 to a liquid refrigerant filter/dryer 72 forremoving any water, acid or particular contaminants that may remainwithin the refrigerant. The purge port of tank 70 is connected to amanual valve 74, and to one input of a double-needle gage 76. The secondinput of gage 76 is connected to bulb 68. Gage 76 thus reads a pressuredifferential between air captured within operator may selectively purgeair from within tank 70 by operation of valve 74. The structure andfunction of such air purge system are disclosed in greater detail U.S.Pat. No. 5,005,369 and U.S. application Ser. No. 07/576,952 assigned tothe assignee hereof, to which reference may be made for further detail.

The outlet side of filter 72 is connected through a moisture indicator78, a check valve 80 and a manual valve 82 to a connector 84 forconnection to the vapor port of a liquid refrigerant storage container86. Valve 58 is also connected to valve 82 through a check valve 88, andvalve 58 is connected to the inlet of evaporator 32 in parallel withflow control valve 30 for selectively clearing refrigerant from coil 60,condenser 62 and coil 64 as described in above-noted U.S. applicationSer. No. 07/681,365.

In operation, connecter 14 is coupled to refrigeration equipment fromwhich refrigerant is to be recovered, and connector 84 is coupled tostorage container 86 as shown. Compressor motor 44 and compressor 42 areenergized, and valve 12 is opened to initiate a refrigerant recoveryoperation. If incoming refrigerant to accumulator 20 is in liquid ormixed liquid/vapor phase, presence of liquid in the accumulator isdetected by sensor 28 and valve 24 is closed. Such liquid refrigerant isfed through valve 30, evaporator 32, oil separator 26 and filter 40 tocompressor 42, and thence from the compressor through oil separator 50,condenser 62, coil 64, air purge tank 70, filter 72, moisture indicator78 and valve 82 to tank 86. On the other hand, if the input refrigerantis entirely in vapor phase or switches from liquid phase to vapor phase,sensor 28 opens valve 24 as soon as all liquid phase refrigerant hasbeen withdrawn from accumulator 20, so that incoming vapor phaserefrigerant is fed directly to oil separator 26 and compressor 42bypassing evaporator 32. In this way, not only is the rate ofrefrigerant recovery greatly enhanced, but superheating of inputrefrigerant already in vapor phase is avoided. When refrigerant has beenfully recovered from the equipment coupled to connector 14, pressuresensor 17 functions to close valve 12 and/or remover energy fromcompressor motor 44.

FIGS. 2 and 3 illustrate modified embodiments of the invention, in whichreference numerals identical to those employed in FIG. 1 indicatecorrespondingly identical parts. In FIG. 2, vapor/liquid separationaccumulator 20 of FIG. 1 is replaced by a sight glass 90 connectedbetween filter 16 and control valve 30, through which an operator mayobserve the phase or phases of input refrigerant. Solenoid valve 24 isconnected between sight glass 90 and the inlet of oil separator 26, andis controlled by a manual switch 92 connected to a suitable source ofelectrical power (not shown). When the operator observes at sight glass90 that input refrigerant is in liquid or mixed liquid/vapor phase,switch 92 and valve 24 remain open, and all input refrigerant is fed toevaporator 32. On the other hand, when the operator does not observeliquid phase refrigerant at sight glass 90, switch 92 is closed toenergize valve 24 and thereby bypass refrigerant from evaporator 32.

In the embodiment of FIG. 3, evaporator/condenser unit 34 and oilseparator 26 (FIGS. 1 and 2) are replaced by a combinedheat-exchange/oil-separator unit 94. Unit 94 comprises a closedgenerally cylindrical canister 96 having an open internal volume 98 anda condenser coil 100 disposed within the lower portion of volume 98. Apair of liquid ports and a pair of vapor ports are provided at the upperend of canister 94. To the extent thus far described,heat-exchange/oil-separator unit is essentially the same as thatdisclosed in U.S. Pat. Nos. 4,768,347 and 4,809,520 noted above. Theliquid ports of unit 94 are connected to coil 60 of oil separator 50 andchamber 66 (FIG. 1) respectively. One vapor port of unit 94 is connectedto the inlet side of filter 40.

A first liquid level sensor 102 is positioned within canister 96 closelyadjacent to but just above condenser coil 100 for sensing whenrefrigerant just covers the condenser coil. A second liquid refrigerantlevel sensor 104 is positioned beneath sensor 102 for sensing a lowerlevel of liquid refrigerant within canister 96. Sensor 102 isoperatively coupled to a first solenoid valve 106 for feedingrefrigerant to the input port of canister 96. Sensor 104 is operativelycoupled to a second solenoid valve 108 connected in parallel with valve106. Valve 106 has a relatively restricted flow passage for selectivelyadmitting liquid phase refrigerant, or mixed liquid/vapor phaserefrigerant, to canister 96 under control of sensor 102. When sensor 102detects that liquid refrigerant is below the level of the sensor, sensor102 automatically opens valve 106 to admit additional liquid refrigerantto bring the refrigerant level backup to the position of the sensor, atwhich point valve 106 is closed.

On the other hand, valve 108 is configured to have a relatively largerefrigerant flow passage for admitting refrigerant in vapor phase undercontrol of sensor 104. That is, when the level of refrigerant withinvolume 98 falls below the level of sensor 104, absence of input liquidphase refrigerant is inferred, and sensor 104 opens valve 108 forhigh-volume admission of refrigerant in vapor phase. Vapor phaserefrigerant, either as admitted through valves 106, 108 or as evaporatedfrom liquid phase refrigerant within the lower portion of canister 96,exits the canister through the second vapor port, and is fed to filter40 and thence to compressor 42 (FIG. 1) as previously described. Thus,input refrigerant flow is controlled by sensors 102, 104 and valves 106,108 as a function of refrigerant phase to maximize the refrigerantthroughput without over flowing the heat exchange unit.

We claim:
 1. A refrigerant handling system that includes a compressorhaving an inlet and an outlet, means coupled to said compressor inletfor evaporating refrigerant passing therethrough, input means forconnecting said evaporating means to a source of refrigerant, meanscoupled to said input means for determining presence of liquidrefrigerant at said input means, and means connected between said inputmeans and said compressor inlet in parallel with said evaporating meansfor bypassing refrigerant from said evaporating means to said compressorinlet when liquid refrigerant is absent at said input means,said meansfor determining presence of liquid refrigerant at said input meanscomprising refrigerant accumulation means connected between said inputmeans and said evaporating means having an open internal volume, meanscoupled to said volume for detecting level of liquid refrigeranttherein, and means responsive to said level-detecting means forindicating absence of liquid refrigerant within said volume.
 2. Thesystem set forth in claim 1 wherein said refrigerant bypassing meanscomprises a refrigerant valve and means for opening said valve in theabsence of liquid refrigerant at said inlet means.
 3. The system setforth in claim 1 wherein said bypassing means comprises a solenoidvalve, and wherein said means responsive to said level-detecting meanscomprises means for opening said solenoid valve in the absence of liquidrefrigerant in said volume.
 4. A refrigerant handling system thatincludes a compressor having an inlet and an outlet, means coupled tosaid compressor inlet for evaporating refrigerant passing therethrough,input means for connecting said evaporating means to a source ofrefrigerant, means coupled to said input means for determining presenceof liquid refrigerant at said input means, and means connected betweensaid input means and said compressor inlet in parallel with saidevaporating means for bypassing refrigerant from said evaporating meansto said compressor inlet when liquid refrigerant is absent at said inputmeans, said refrigerant bypassing means comprising a refrigerant valveand means for opening said valve in the absence of liquid refrigerant atsaid input means.
 5. The system set forth in claim 4 wherein said meansfor determining presence of liquid refrigerant at said input meanscomprises refrigerant accumulation means connected between said inputmeans and said evaporating means having an open internal volume, meanscoupled to said volume for detecting level of liquid refrigeranttherein, and means responsive to said level-detecting means forindicating absence of liquid refrigerant within said volume.
 6. Thesystem set forth in claim 5 wherein said valve comprises a solenoidvalve, and wherein said means responsive to said level-detecting meanscomprises means for opening said solenoid valve in the absence of liquidrefrigerant in said volume.
 7. The system set forth in claim 4 whereinsaid means for determining presence of liquid refrigerant at said inputmeans comprises a sight glass connected between said input means andsaid evaporating means for visual observation of liquid refrigerantflowing to said evaporating means.
 8. The system set forth in claim 7wherein said means for opening said valve comprises means for manuallyopening said valve in the absence of liquid refrigerant at said sightglass.
 9. The system set forth in claim 4 further comprising condensermeans coupled to said compressor outlet in heat exchange relationshipwith said evaporating means.
 10. The system set forth in claim 9 furthercomprising a refrigerant storage container connected to receiverefrigerant from said condenser means.
 11. A refrigerant recovery systemthat includes a refrigerant compressor having an inlet and an outlet,input means for connection to refrigeration equipment from whichrefrigerant is to be recovered, means connected between said input meansand said compressor inlet for evaporating refrigerant passingtherethrough, a refrigerant storage container, condenser means coupledbetween said compressor outlet and said storage container for at leastpartially condensing refrigerant fed to said storage container, meanscoupled to said input means for detecting absence of liquid refrigerantat said input means, and means coupled to said absence-detecting meansfor selectively controlling flow of refrigerant from said input means tosaid compressor inlet.
 12. The system set forth in claim 11 wherein saidabsence-detecting means comprises means having an open internal volumeconnected to said input means, means coupled to said volume fordetecting level of liquid refrigerant therewithin, and means forindicating absence of liquid at said input means as an function ofliquid refrigerant level in said volume.
 13. The system set forth inclaim 12 wherein said means for selectively controlling flow ofrefrigerant comprises a solenoid valve connected between said inputmeans and said compressor inlet, and means operatively coupling saidsolenoid valve to said level-detecting means for opening said valve inthe absence of liquid refrigerant at said input means.
 14. The systemset forth in claim 13 wherein said solenoid valve is operativelyconnected between said input means and said compressor inlet, and isresponsive to absence of liquid refrigerant at said level-detectingmeans for feeding refrigerant from said input means to said compressorinlet bypassing said evaporator means.
 15. The system set forth in claim13 wherein said evaporating means and said means having an open internalvolume are combined is a unitary construction.
 16. The system set forthin claim 15 wherein said condenser means comprises a condenser coildisposed in heat exchange relationship with refrigerant in said volume.17. The system set forth in claim 13 wherein said condenser means isdisposed in heat exchanger relationship with said evaporating means. 18.The system set forth in claim 11 wherein said means for selectivelycontrolling refrigerant flow comprises a refrigerant valve and means foropening said valve in the absence of liquid refrigerant at said inputmeans.
 19. The system set forth in claim 18 wherein said means fordetecting absence of liquid refrigerant at said input means comprises asight glass connected between said input means and said evaporatingmeans for visual observation of liquid refrigerant flowing to saidevaporating means.
 20. The system set forth in claim 19 wherein saidmeans for opening said valve comprises means for manually opening saidvalve in the absence of liquid refrigerant at said sight glass.
 21. Arefrigerant handling system that includes a compressor having an inletand an outlet, input means for connection to a source of refrigerant,refrigerant evaporator means including means having an open internalvolume coupled to said compressor inlet, refrigerant condenser meansincluding a refrigerant coil disposed within a lower portion of saidvolume, first liquid refrigerant level detection means coupled to saidvolume for detecting a level of refrigerant at an upper end of said coilcovering said coil, and flow control means disposed between said inputmeans and said volume and responsive to said level-detecting means forrestricting flow of refrigerant to said volume while maintaining levelof liquid refrigerant covering said coil for optimum heat exchange withsaid coil.
 22. The system set forth in claim 21 wherein said flowcontrol means comprises a control valve for admitting refrigerant tosaid volume when level of liquid refrigerant in said volume is belowsaid first level-detecting means and termination flow of refrigerant tosaid volume when level of liquid refrigerant is at said firstlevel-detection means.
 23. The system set forth in claim 22 wherein saidvalve comprises a solenoid valve responsive to said first leveldetecting means for automatically admitting and terminating flow ofrefrigerant to said volume.
 24. The system set forth in claim 22 whereinsaid flow control means further comprises second liquid refrigerantlevel detection means coupled to said volume for detecting a level ofliquid refrigerant lower then said first level detection means, andmeans responsive to said second level detection means for increasingflow of refrigerant to said volume.
 25. The system set forth in claim 24wherein said means responsive to said second level detection meanscomprises a second flow control valve connected in parallel with saidfirst flow control valve.
 26. The system set forth in claim 22 whereinsaid first level detector means comprises a liquid refrigerant sensorpositioned when said volume adjacent to said upper end of said coil.